Rough boxes

Create sketchy random borders, as if they were drawn by hand. No extra element, fully responsive

P CSS Painting API

C+ CSS Properties and Values API (CSS.registerProperty)

This demo produces different result on each repaints (resize browser, zoom, play with controls, etc.), as there is no way to store state inside the registered paint. More info in this TC39 proposal about Seeded Random numbers from Tab Atkins.